1. Field of the Invention
The present invention relates to a multiprobe formed by providing a plurality of cantilevers on the same body in such a manner to allow selective use of each cantilever and to a scanning probe microscope utilizing the same.
2. Description of the Related Art
In scanning probe microscopes that are conventionally used for finding changes in a surface configuration, a physical quantity and the like of a microscopic region on the order of atoms, a probe which has a scanning needle on an end thereof or which has no such needle has been used as a scanning probe. In general, a probe of this type is fabricated in a cantilevered configuration to measure a configuration or the like of a surface of a sample by detecting the deflection of a cantilever due to an attraction force or repulsion force originating from an interatomic force generated between the surface of the sample and the scanning needle while when the cantilever is scanned across the sample surface.
A cantilever as described above must be replaced with a new one appropriately depending on the period of use because it is a wearable component, and it may be required to modify the cantilever depending on the purpose of measurement. There has been a problem in that the replacement of a probe is difficult and troublesome because it is a very small component. In order to solve this problem, multiprobes have been used which are formed by providing a plurality of cantilevers on the same body.
Known configurations of conventional multiprobes used for such a purpose include a configuration wherein a piezoelectric element for switching is provided for each of a plurality of cantilevers provided on the same body and those piezoelectric elements are selectively driven to allow only a desired cantilever to scan a surface of a sample and a configuration wherein a plurality of cantilevers are provided with different lengths and are sequentially used in the order of their decreasing lengths with cantilevers once used being broken and removed (or wherein long cantilevers are broken to prevent them from hindering the use of a desired cantilever).
However, the above-described known configurations have a problem in that the cost of a probe is increased by a complicated structure and operation attributable to the need for a switching mechanism utilizing a piezoelectric material such as ZnO and PZT and in that a need for a control system for selecting cantilevers leads to an increase in cost.
The latter configuration also has a problem in that the need for breaking unnecessary cantilevers reduces ease of operation and in that cantilevers can be broken by mistake when unnecessary cantilevers are broken because the component is very small and this makes it difficult to treat the component.
It is an object of the invention to provide a multiprobe in which the above-described problems with the prior art can be solved and a scanning probe microscope utilizing the same.
In order to solve the above-described problems, according to the invention, there is provided a multiprobe used as a scanning probe of a scanning probe microscope formed by providing a plurality of cantilevers on the same body, characterized in that the plurality of cantilevers have resonance frequencies different from each other and in that portions of the plurality of cantilevers to contact with a sample are arranged in a substantially liner configuration.
Since the plurality of cantilevers provided on the same body have resonance frequencies different from each other, when the multiprobe is operated in a DFM mode, it is possible to put only a required cantilever close to a surface of a sample to involve it in measurement by applying vibrations having the resonance frequency of the cantilever required for the measurement to the multiprobe thereby causing only the required cantilever to vibrate with an amplitude greater than those of the rest of the cantilevers as a result of resonance. That is, the multiprobe is operated in a DFM mode; the plurality of cantilevers are provided with peaks of resonance which are different from each other to such a degree that an operating point can be fixed; and the frequency of vibrations for external excitation is made substantially equal to the resonance frequency of a cantilever to be selected to involve only the cantilever in measurement as a result of an increased vibration amplitude. This makes it very easy to operate the plurality of cantilevers selectively.
While it is not required to provide each of the cantilevers with a scanning needle, since portions of the cantilevers to contact with a surface of a sample are arranged in a substantially linear configuration, the contact portions of those cantilevers are at similar distances to the sample during approach.
A self-detection type probe may be provided having a configuration as described above in which each of the plurality of cantilevers incorporates a distortion sensor for detecting deflection of the cantilever. In this case, the distortion sensors are set at the same characteristics.
The present invention proposes a method of measurement in which the distortion sensor of at least one cantilever uninvolved in measurement is used as a reference distortion sensor for measuring the output of the distortion sensors of the cantilevers involved in the measurement to improve the signal-to-noise ratio of the measurement.
An alternative configuration is possible in which a reference cantilever is separately provided and in which the reference cantilever is equipped with a distortion sensor similar to those of cantilevers for measurement as a reference distortion sensor.
The present invention proposes a scanning probe microscope which utilizes a multiprobe as described above and in which cantilevers can be selected and switched by substantially matching the frequency of vibration applied to the multiprobe with resonance frequency of a desired cantilever of the multiprobe.